The present invention relates to a veneer lathe which includes drive rolls provided ahead of the knife. More particularly, the present invention relates to a veneer lathe which includes drive rolls, capable of being adjusted horizontally and vertically.
Conventionally, a veneer lathe having drive rolls provided for exerting external force onto the log surface ahead of the tangential knife in order to reduce load on the log core is known. (See U.S. patent application Ser. No. 861,278). The drive rolls carry a plurality of spikes around their periphery. These spikes cut into the log surface and rotate the log as the rolls are driven by a motor.
As the cutting operation advances, however, the quality of the log wood into which the spikes cut becomes progressively poorer. As a result, such spike engagement can mar the surface quality since the wood cannot withstand the spike forces.
In addition, other problems are found in the conventional veneer lathe as the log diameter decreases with the advance of cutting operation. First, the depth of spike cuts into the log wood becomes smaller. Second, the number of those spikes engaging decreases. Third, the pressure exerted on the log surface ahead of the knife edge by the pressure bars and pressure rollers, decreases. Referring to FIG. 1, circle A represents a large diameter log, circle B a small diameter log, and circle C a drive roll or a pressure roller. The spike piercing depth, the number of piercing spikes, and the pressure exerted on the log wood ahead of the knife edge at the initial stage of the cutting operation are represented by area D defined by the intersection of circles A and circle C. Later stage conditions are represented by area E defined by the intersection of circle B and circle C. As shown, area E is smaller than area D. This area represents detrimental phenomena observed in a conventional veneer lathe.